The present invention relates generally to substrate processing systems, and, in particular, to a multi-function chamber for a substrate processing system.
Glass substrates are being used for applications such as active matrix television and computer displays, among others. Each glass substrate can form multiple display monitors each of which contains more than a million thin film transistors.
The processing of large glass substrates often involves the performance of multiple sequential steps, including, for example, the performance of chemical vapor deposition (CVD) processes, physical vapor deposition (PVD) processes, or etch processes. Systems for processing glass substrates can include one or more process chambers for performing those processes.
The glass substrates can have dimensions, for example, of 550 mm by 650 mm. The trend is toward even larger substrate sizes, such as 650 mm by 830 mm and larger, to allow more displays to be formed on the substrate or to allow larger displays to be produced. The larger sizes place even greater demands on the capabilities of the processing systems.
Some of the basic processing techniques for depositing thin films on the large glass substrates are generally similar to those used, for example, in the processing of semiconductor wafers. Despite some of the similarities, however, a number of difficulties have been encountered in the processing of large glass substrates that cannot be overcome in a practical way and cost effectively by using techniques currently employed for semiconductor wafers and smaller glass substrates.
For example, efficient production line processing requires rapid movement of the glass substrates from one work station to another, and between vacuum environments and atmospheric environments. The large size and shape of the glass substrates makes it difficult to transfer them from one position in the processing system to another. As a result, cluster tools suitable for vacuum processing of semiconductor wafers and smaller glass substrates, such as substrates up to 550 mm by 650 mm, are not well suited for the similar processing of larger glass substrates, such as 650 mm by 830 mm and above. Moreover, cluster tools require a relatively large floor space.
Similarly, chamber configurations designed for the processing of relatively small semiconductor wafers are not particularly suited for the processing of these larger glass substrates. The chambers must include apertures of sufficient size to permit the large substrates to enter or exit the chamber. Moreover, processing substrates in the process chambers typically must be performed in a vacuum or under low pressure. Movement of glass substrates between processing chambers, thus, requires the use of valve mechanisms which are capable of closing the especially wide apertures to provide vacuum-tight seals and which also must minimize contamination.
Furthermore, relatively few defects can cause an entire monitor formed on the substrate to be rejected. Therefore, reducing the occurrence of defects in the glass substrate when it is transferred from one position to another is critical. Similarly, misalignment of the substrate as it is transferred and positioned within the processing system can cause the process uniformity to be compromised to the extent that one edge of the glass substrate is electrically non-functional once the glass has been formed into a display. If the misalignment is severe enough, it even may cause the substrate to strike structures and break inside the vacuum chamber.
Other problems associated with the processing of large glass substrates arise due to their unique thermal properties. For example, the relatively low thermal conductivity of glass makes it more difficult to heat or cool the substrate uniformly. In particular, thermal losses near the edges of any large-area, thin substrate tend to be greater than near the center of the substrate, resulting in a non-uniform temperature gradient across the substrate. The thermal properties of the glass substrate combined with its size, therefore, makes it more difficult to obtain uniform characteristics for the electronic components formed on different portions of the surface of a processed substrate. Moreover, heating or cooling the substrates quickly and uniformly is more difficult as a consequence of its poor thermal conductivity, thereby reducing the ability of the system to achieve a high throughput.
Depending on the functions or processes to be performed within a particular process chamber, pre-poscessing or post-processing, such as heating or cooling of a substrate, may be required. Such pre-processing and post-processing functions may be performed in chambers separate from a primary process chamber. Due to the various functions that a particular chamber is designed to perform, each chamber may be configured differently from other chambers. Moreover, once a chamber is designed to perform a particular function, such as pre-process heating of the substrate, it may not be possible to reconfigure the chamber to perform another different function, such as post-process cooling of the substrate. Such designs can limit the flexibility offered by a given chamber.
In general, according to one aspect, an evacuable chamber includes a chamber body having an aperture to allow a substrate to be;transferred into or out of the chamber. The chamber is configurable using removable components in at least two of the following configurations: a base configuration for .providing a transition between two different pressure, a heating configuration for heating the substrate and providing a transition between two different pressures, and a cooling configuration for cooling the substrate and providing a transition between two different pressures.
When the chamber is configured in the base configuration, the chamber includes at least one removable volume reducing element. The removable volume reducing elements can be made, for example, of plastic, aluminum or other vacuum-compatible material. One volume reducing element can be positioned adjacent and below a lid of the chamber. Another volume reducing element can be positioned adjacent and above the bottom interior surface of the chamber.
When configured in the heating configuration, the chamber includes an upper heating assembly and a heating platen. The upper heating assembly can be disposed between a lid of the chamber and a substrate support mechanism. The heating platen can be movable to lift a substrate positioned on the support mechanism to a heating position below the upper heating assembly, and to lower the substrate from the heating position onto the support mechanism.
The heating platen can include inner and outer heating loops whose temperatures are independently controllable. For example, during operation, the temperature of the outer loop can be maintained at a higher temperature than the inner loop. The heating platen also can have an upper surface having a pattern of horizontal channels designed to control a contact area between a substrate and the heating platen when the substrate is supported on the upper surface of the platen. For example, the concentration of channels can be greater near the center of the platen than near its perimeter.
The upper heating assembly can have a stationary plate with inner and outer heating loops whose temperatures can be controlled independently of one another. A gas delivery tube can be attached to the chamber, and the stationary plate can include a series of vertical holes to allow a gas to be delivered from the delivery tube to an interior region of the chamber via the vertical holes. The upper heating assembly also can have a diffusion screen disposed between the stationary plate and the substrate heating position.
Various of the foregoing features can help compensate for thermal losses near the edges of a large glass substrate and can provide a more uniform temperature across the substrate when the chamber is configured in the heating configuration.
The heating configuration also can be used to perform ashing processes.
When configured in the cooling configuration, the chamber can include a cooling platen and may also include an upper cooling assembly. When an upper cooling assembly is employed, it can be disposed between a lid of the chamber and a substrate support mechanism. The cooling platen can be movable to lift a substrate positioned on the support mechanism to a cooling position below the upper cooling assembly, and to lower the substrate from the cooling position onto the support mechanism.
The cooling platen can include multiple cooling tubes through which a cooling fluid can flow. In one implementation, the concentration of cooling tubes near the center of the platen can be greater than the concentration near the perimeter. The cooling platen can have an upper surface with a pattern of horizontal channels designed to control a contact area between a substrate and the cooling platen when the substrate is supported on the upper surface of the platen. In one implementation, the concentration of channels near the perimeter of the cooling platen is greater than near the center.
The upper cooling assembly also can have a stationary plate with multiple cooling tubes through which a cooling fluid can be provided to flow. In some implementations, the concentration of cooling channels is greater near the center of the stationary plate than near the perimeter. A gas delivery tube can be attached to the chamber. The stationary plate includes a series of vertical holes to allow a gas to be delivered from the delivery tube to an interior region of the chamber via the vertical holes. The upper cooling assembly further can include a diffusion screen disposed between the stationary plate and the substrate cooling position.
Various of the foregoing features can help compensate for, or take into account, thermal losses near the edges of a large glass substrate and can provide a more uniform temperature across the substrate when the chamber is configured in the cooling configuration.
Resistive elements can be provided to heat the chamber body and the lid to maintain them within a specified temperature range and to compensate for thermal losses near the substrate edges. The resistive elements can be used, for example, when the chamber is configured as a cooling chamber.
Water cooling can be provided to the chamber body and lid when the chamber is configured as a heating chamber if removal of excess heat is necessary to limit and control temperature.
In yet a further aspect, a load lock chamber includes a chamber body having an aperture to allow a substrate to be transferred into or out of the chamber; and a thermally conductive platen for supporting a substrate within the chamber. The platen has multiple zones for preferentially changing the temperature of the substrate by conduction so as to compensate for thermal losses near edges of the substrate.
In addition, a method of processing a substrate in a load lock chamber includes supporting the substrate on a substrate support mechanism within the chamber and changing the pressure in the chamber from a first pressure to a second pressure. The method further includes controlling various surface temperatures in the chamber to compensate for, or take into account, thermal losses near edges of the substrate.
Various implementations include one or more of the following advantages. A single load lock chamber can be configured in multiple configurations depending on the requirements of the particular substrate process system. The chamber design, therefore, facilitates changes in system design because the chamber can be re-configured relatively easily and quickly. Furthermore, the various configurations of the chamber allow transitions between first and second pressures, such as atmospheric and process pressures, to be performed quickly.
Various features also enable a large glass substrate to be cooled or heated quickly, thereby increasing the throughput of the system. Depending on the particular configuration used, various features of the chamber design help compensate for thermal losses near the substrate edges to provide a more uniform temperature across substrate. Various features also can help maintain the edges of a substrate in compression which can reduce the likelihood of substrate breakage during heating, cooling and other processes.
Additionally, the disclosed techniques for distributing a gas throughout the chamber provide improvements over prior techniques, which were not well suited for handling large substrates.
Other features and advantages will be apparent from the following detailed description, drawings and claims.